Little is known about factors controlling kinetics of aerosol dispersion and deposition in the lung periphery. This knowledge becomes increasingly important in many fields such as environmental and occupational exposures, cigarette smoke, diagnostic applications, drug delivery, and gene therapy. The ultimate goal of this project is to improve understanding of basic physics of aerosol kinetics in the acinus. Specifically, I will test the hypothesis that the complex structure of the alveolar duct plays an important role in aerosol deposition and dispersion processes. A computational Monte Carlo analysis of aerosol kinetics is proposed. Dynamic behavior of aerosol particles will be described by the Langevin equation (Newton's second law of motion including random Brownian force) and their trajectories will be computed by successively integrating the Langevin equation. Conditional probabilities of trajectories for a given initial condition will be analyzed. Based on these analyses, the deposition and dispersion processers in alveolated ducts will be studied over physiologically relevant conditions. Preliminary results indicate a strong influence of structure upon local deposition fraction, upon the markedly nonuniform pattern of deposition within the alveolus, and upon aerosol bolus mixing with resident gas. By comparing the predictions for aerosol behavior in the alveolated duct with those in an equivalent straight tube and with the results of existing experimental observation in animal studies (e.g. Zeltner, et al., J. Appl. Physiol. 70(3):, 1137-1145), the significance of structural complexity on aerosol kinetics will be quantified. Governing-parameters will also be identified, helping to elucidate the underlying mechanisms for these phenomena. In addition, basic predictions of this analysis will be tested experimentally using benchtop physical models. The results of this study will enrich fundamental knowledge of the physics of aerosol deposition and mixing processes in lung periphery and provide important information bearing upon the validity of past analyses of aerosol kinetics.